Wiring circuit board

Abstract

The wiring circuit board (1) includes: a base insulating layer (2); a conductor layer (3) disposed on one side of the base insulating layer (2) in the thickness direction; a cover insulating layer (4) disposed on one side of the base insulating layer (2) in the thickness direction to cover the conductor layer (3); and a shielding layer (5) disposed on the other side of the base insulating layer (2) in the thickness direction and on both sides in the width direction, and disposed on one side of the cover insulating layer (4) in the thickness direction and on both sides in the width direction. At least one of the base insulating layer (2) and the cover insulating layer (4) has a porous resin layer (10).

Description

Technical Field

[0001] This invention relates to a wiring circuit board. Background Technology

[0002] In the past, coaxial cables were used as electrical transmission lines.

[0003] For example, a coaxial cable for high-frequency power transmission is proposed, comprising: a conductor; a jacket layer (insulation layer) disposed on the outer peripheral surface of the conductor; and a shielding layer disposed on the outer peripheral surface of the jacket layer (see, for example, Patent Document 1 below). In the coaxial cable for high-frequency power transmission described in Patent Document 1, the jacket layer is made of solid cross-linked polyethylene resin.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-22146 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In recent years, there has been a growing demand for higher transmission efficiency and thinner profiles for coaxial cables used in high-frequency power transmission.

[0009] However, in the coaxial cable for high-frequency power transmission described in Patent Document 1, since the jacket layer is made of solid cross-linked polyethylene resin, there is a limit to the improvement of transmission efficiency.

[0010] Furthermore, the high-frequency power transmission coaxial cable described in Patent Document 1 already has the structure of a coaxial cable, thus it is difficult to make it thinner.

[0011] This invention provides a wiring circuit board that can improve the transmission efficiency of high-frequency signals and achieve a thinner profile.

[0012] Solution for solving the problem

[0013] The present invention (1) provides a wiring circuit board, wherein the wiring circuit board comprises: a substrate insulating layer; a conductor layer disposed on one side of the substrate insulating layer in the thickness direction; a cover insulating layer disposed on one side of the substrate insulating layer in the thickness direction in a manner covering the conductor layer; and a shielding layer disposed on the other side of the substrate insulating layer in the thickness direction and on both sides in the width direction, and disposed on one side of the cover insulating layer in the thickness direction and on both sides in the width direction, wherein at least one of the substrate insulating layer and the cover insulating layer has a porous resin layer.

[0014] The present invention (2) includes the wiring circuit board described in (1), wherein the ratio of the distance T2 between one side of the conductor layer in the thickness direction and one side of the covering insulating layer in the thickness direction to the distance T1 between the other side of the conductor layer in the thickness direction and the other side of the base insulating layer in the thickness direction, i.e., T2 / T1, is 0.9 or more and 1.1 or less.

[0015] The present invention (3) includes the wiring circuit substrate described in (1) or (2), wherein the porous resin layer has an independent bubble structure.

[0016] The present invention (4) comprises a wiring circuit board as described in any one of (1) to (3), wherein the porosity of the porous resin layer is 50% or more.

[0017] The present invention (5) comprises a wiring circuit substrate as described in any one of (1) to (4), wherein the porous resin layer is made of polyimide resin.

[0018] The present invention (6) comprises a wiring circuit board as described in any one of (1) to (5), wherein the substrate insulating layer and the cover insulating layer are composed of a porous resin layer.

[0019] The present invention (7) comprises a wiring circuit board according to any one of (1) to (6), wherein the substrate insulating layer is composed of the porous resin layer, and the covering insulating layer comprises: an adhesive layer that contacts one side in the thickness direction and two sides in the width direction of the conductor layer, and contacts a portion of one side in the thickness direction of the substrate insulating layer that does not overlap with the conductor layer when projected along the thickness direction; and the porous resin layer that contacts one side in the thickness direction of the adhesive layer.

[0020] The effects of the invention

[0021] In the wiring circuit board of the present invention, since at least one of the base insulating layer and the cover insulating layer has a porous resin layer, the transmission efficiency of high-frequency signals can be improved.

[0022] The base insulating layer and the cover insulating layer of the wiring circuit board of the present invention are layered, thus enabling thinning. Attached Figure Description

[0023] [ Figure 1 ] Figure 1 This is a cross-sectional view of the first embodiment of the wiring circuit board of the present invention.

[0024] [ Figure 2 ] Figure 2 A~ Figure 2 F is Figure 1 The diagram shows the manufacturing process of the wiring circuit board. Figure 2A indicates the process of preparing the other side's shielding layer and base insulation layer. Figure 2 B indicates the process of configuring the conductor layer. Figure 2 C indicates the process of configuring the covering insulation layer. Figure 2 D indicates the process of configuring a shielding layer on one side. Figure 2 E indicates the process of forming the opening. Figure 2 F indicates the process of configuring the side shielding layer.

[0025] [ Figure 3 ] Figure 3 yes Figure 1 A cross-sectional view of a modified example of a wiring circuit board (a configuration in which the conductor layer contains multiple wirings).

[0026] [ Figure 4 ] Figure 4 This is a cross-sectional view of the second embodiment of the wiring circuit board of the present invention (the covering insulating layer includes a porous resin layer and an adhesive layer).

[0027] [ Figure 5 ] Figure 5 A~ Figure 5 D is Figure 4 The diagram shows the manufacturing process of the wiring circuit board. Figure 5 A represents the process of preparing the adhesive layer. Figure 5 B indicates the process of bringing the insulating layer into contact with the adhesive layer. Figure 5 C represents the process of forming the opening. Figure 5 D indicates the process of configuring the side shielding layer.

[0028] [ Figure 6 ] Figure 6 yes Figure 4 A cross-sectional view of a modified example of a wiring circuit board (a configuration in which the conductor layer contains multiple wirings). Detailed Implementation

[0029] <First Embodiment>

[0030] Reference Figure 1 The first embodiment of the wiring circuit board of the present invention will be described below.

[0031] like Figure 1As shown, the wiring circuit board 1 is, for example, a transmission line for transmitting signals (electrical signals), preferably a high-frequency transmission line (cable for transmitting high-frequency signals) for transmitting high-frequency signals (specifically, signals with a frequency of 1 GHz or higher, further, signals with a frequency of 2 GHz or higher, and signals with a frequency of 100 GHz or lower). The wiring circuit board 1 has a flat strip shape extending along the transmission direction. Furthermore, in a cross-sectional view orthogonal to the transmission direction, the wiring circuit board 1 has a predetermined thickness and a generally rectangular shape extending along the width direction (a direction orthogonal to the transmission direction and the thickness direction). The wiring circuit board 1 includes a base insulating layer 2, a conductor layer 3, a cover insulating layer 4, and a shielding layer 5.

[0032] The substrate insulating layer 2 has a generally rectangular shape when viewed in cross-section, which is longer in the width direction.

[0033] The thickness T1 of the substrate insulating layer 2 is the distance T1 between the other side of the conductor layer 3 in the thickness direction and the other side of the substrate insulating layer 2 in the thickness direction. Specifically, the thickness T1 of the substrate insulating layer 2 is, for example, 10 μm or more, preferably 30 μm or more, and also, for example, 200 μm or less, preferably 75 μm or less. In addition, the ratio (T1 / T0) of the thickness T1 of the substrate insulating layer 2 to the thickness T0 of the wiring circuit board 1 is, for example, 0.15 or more, preferably 0.3 or more, and also, for example, 0.6 or less, preferably 0.45 or less.

[0034] The width W1 of the substrate insulating layer 2 is the distance W1 between the two sides of the substrate insulating layer 2 in the width direction. Specifically, the width W1 of the substrate insulating layer 2 is, for example, 100 μm or more, preferably 250 μm or more, and also, for example, 500 μm or less, preferably 350 μm or less. The ratio (W1 / W0) of the width W1 of the substrate insulating layer 2 to the width W0 of the wiring circuit board 1 is, for example, 0.8 or more, preferably 0.9 or more, and also, for example, 1 or less, preferably 0.99 or less.

[0035] The ratio (T1 / W1) of the thickness T1 of the substrate insulating layer 2 to the width W1 of the substrate insulating layer 2 is, for example, 2.0 or less, preferably 1.5 or less, more preferably 1.0 or less, and also, for example, 0.1 or more.

[0036] If the size of the substrate insulating layer 2 is within the above range, the wiring circuit board 1 can improve the transmission efficiency of high-frequency signals and achieve thinning.

[0037] The substrate insulating layer 2 is a porous resin layer 10 (refer to...) Figure 1(The content in parentheses). The porous resin layer 10 has many fine pores (vents). The porous resin layer 10 preferably has an independent bubble structure. When the porous resin layer 10 has an independent bubble structure, the transmission efficiency of high-frequency signals in the wiring circuit board 1 can be improved.

[0038] The porosity of the porous resin layer 10 of the substrate insulating layer 2 is, for example, 50% or more, preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and for example, less than 100%. The porosity of the porous resin layer 10 is measured according to the content described in International Publication No. 2018 / 186486. If the porosity of the porous resin layer 10 is above the aforementioned lower limit, the transmission efficiency of high-frequency signals in the wiring circuit board 1 can be improved.

[0039] The average pore size of the porous resin layer 10 of the substrate insulating layer 2 is, for example, 10 μm or less, preferably 5 μm or less, and also, for example, 0.1 μm or more, preferably 1 μm or more. The average pore size of the porous resin layer 10 is measured according to the description in International Publication No. 2018 / 186486.

[0040] The porous resin layer 10 used as the base insulating layer 2 can be made of, for example, thermosetting resins, thermoplastic resins, and other resins. Thermosetting resins are preferred.

[0041] Examples of thermosetting resins include polycarbonate resins, polyimide resins (thermosetting polyimide resins), thermosetting fluorinated polyimide resins, epoxy resins, phenolic resins, urea-formaldehyde resins, melamine resins, diallyl phthalate resins, silicone resins, thermosetting polyurethane resins, fluoropolymers (polymers containing fluorinated olefins, specifically polytetrafluoroethylene (PTFE), etc.), and liquid crystal polymers (LCPs). These can be used individually or in combination of two or more. Polyimide resins are preferred. If the porous resin layer 10 is made of polyimide resin, low cost and low dielectric constant can be ensured, and the transmission characteristics of high-frequency signals in the wiring circuit board 1 can be improved.

[0042] The dielectric constant of the substrate insulating layer 2 at a frequency of 10 GHz is, for example, 3.0 or less, preferably 2.5 or less, and more preferably 2.0 or less.

[0043] The conductor layer 3 is disposed on one side of the substrate insulating layer 2 in the thickness direction. Specifically, the conductor layer 3 is in contact with the central portion of one side of the substrate insulating layer 2 in the thickness direction. The conductor layer 3 is, for example, a wiring 13.

[0044] In cross-section, the ratio (L2 / L1) of the length L2 of the other side portion 12 of the substrate insulating layer 2 located on the side opposite to the center of the side portion 11 (the portion in contact with the conductor layer 3) in the thickness direction to the length L1 of the other side portion 11 of the substrate insulating layer 2 located on the side opposite to the center of the side portion 11 in the thickness direction (the portion in contact with the conductor layer 3) in the width direction is, for example, 0.9 or more, preferably 0.95 or more, and for example, 1.1 or less, preferably 1.05 or less. The length L1 of one side portion 11 and the length L2 of the other side portion 12 of the substrate insulating layer 2 are preferably approximately the same. If the dimensions of one side portion 11 and the other side portion 12 are within the above range, the wiring circuit board 1 can improve the transmission efficiency of high-frequency signals and achieve a thinner profile.

[0045] The wiring 13 has a roughly rectangular shape when viewed in cross-section, which is longer in the width direction.

[0046] The material of conductor layer 3 is not particularly limited; for example, metals such as copper, iron, silver, gold, aluminum, nickel, and their alloys (stainless steel, bronze) can be included. From the viewpoint of obtaining lower resistance, copper and gold are preferred.

[0047] The thickness T3 of the conductor layer 3 is, for example, 0.1 μm or more, preferably 1 μm or more, and also, for example, 100 μm or less, preferably 50 μm or less. The ratio (T3 / T0) of the thickness T3 of the conductor layer 3 to the thickness T0 of the wiring circuit substrate 1 is, for example, 0.5 or less, preferably 0.3 or less, more preferably 0.2 or less, and also, for example, 0.01 or more, preferably 0.05 or more.

[0048] The width W3 of the conductor layer 3 (wiring 13) is smaller than the width W1 of the substrate insulating layer 2. The width W3 of the conductor layer 3 is, for example, 5 μm or more, preferably 10 μm or more, and also, for example, 200 μm or less, preferably 100 μm or less. The ratio (W3 / W1) of the width W3 of the conductor layer 3 to the width W1 of the substrate insulating layer 2 is, for example, 0.75 or less, preferably 0.50 or less, more preferably 0.25 or less, and also, for example, 0.01 or more, preferably 0.05 or more. The ratio (T3 / W3) of the thickness T3 of the conductor layer 3 to the width W3 of the conductor layer 3 is, for example, 0.75 or less, preferably 0.5 or less, and also, for example, 0.01 or more, preferably 0.01 or more.

[0049] If the size of the conductor layer 3 is within the above range, the wiring circuit board 1 can improve the transmission efficiency of high-frequency signals and achieve thinning.

[0050] Conductor layer 3 is a solid, dense layer. Therefore, the porosity of conductor layer 3 is essentially 0%.

[0051] The covering insulating layer 4 is disposed on one side of the base insulating layer 2 in the thickness direction, covering the conductor layer 3. Specifically, the covering insulating layer 4 contacts the portion of the base insulating layer 2 located around the conductor layer 3 on one side in the thickness direction, and contacts both the thickness direction side and the width direction sides of the conductor layer 3. Furthermore, the portion of the base insulating layer 2 located around the conductor layer 3 is the portion of the base insulating layer 2 that does not overlap with the conductor layer 3 when projected along the thickness direction. The covering insulating layer 4 has a roughly U-shaped form when viewed in section, opening towards the other side in the thickness direction. The thickness direction side of the covering insulating layer 4 is flat. The width direction sides of the covering insulating layer 4 are flush with the width direction sides of the base insulating layer 2, respectively.

[0052] The thickness T2 of the covering insulating layer 4 is the distance T2 between one side of the conductor layer 3 in the thickness direction and one side of the covering insulating layer 4 in the thickness direction. The thickness T2 of the covering insulating layer 4 is, for example, 10 μm or more, preferably 30 μm or more, and also, for example, 200 μm or less, preferably 75 μm or less. Furthermore, the ratio (T2 / T0) of the thickness T2 of the covering insulating layer 4 to the thickness T0 of the wiring circuit board 1 is, for example, 0.15 or more, preferably 0.3 or more, and also, for example, 0.6 or less, preferably 0.45 or less. If the size of the covering insulating layer 4 is within the above range, the wiring circuit board 1 can improve the transmission efficiency of high-frequency signals and achieve a thinner profile.

[0053] The ratio (T2 / T1) of the thickness T2 of the covering insulating layer 4 to the thickness T1 of the base insulating layer 2 is, for example, 0.9 or more, preferably 0.95 or more, and also, for example, 1.1 or less, preferably 1.05 or less. If the ratio (T2 / T1) of the thickness T2 of the covering insulating layer 4 to the thickness T1 of the base insulating layer 2 is above the lower limit and below the upper limit mentioned above, high transmission efficiency of high-frequency signals can be ensured.

[0054] The thickness T1 of the base insulating layer 2 extends from the shielding layer 5 (the other shielding layer 6 described later) facing the base insulating layer 2 to the conductor layer 3. Similarly, the thickness T2 of the covering insulating layer 4 extends from the shielding layer 5 (the other shielding layer 7 described later) facing the covering insulating layer 4 to the conductor layer 3. If their ratio (T2 / T1) is 0.9 or more and 1.1 or less, then the two lengths can be substantially the same. In other words, the thickness T2 of the covering insulating layer 4 can be approximately the same as the thickness T1 of the base insulating layer 2.

[0055] Therefore, the influence of a magnetic field from one side of the thickness direction on the conductor layer 3 can be used to counteract the influence of a magnetic field from the other side of the thickness direction on the conductor layer 3. Thus, the influence of external magnetic fields on the conductor layer 3 can be suppressed. As a result, the wiring circuit board 1 can further improve the transmission efficiency of high-frequency signals.

[0056] The width W2 of the covering insulating layer 4 is the same as the width W1 of the base insulating layer 2. The ratio (W2 / W0) of the width W2 of the covering insulating layer 4 to the width W0 of the wiring circuit board 1 is, for example, 0.8 or more, preferably 0.9 or more, and also, for example, 1 or less, preferably 0.99 or less. The ratio (T2 / W2) of the thickness T2 of the covering insulating layer 4 to the width W2 of the covering insulating layer 4 is, for example, 2.0 or less, preferably 1.5 or less, more preferably 1.0 or less, and also, for example, 0.1 or more. If the size of the covering insulating layer 4 is within the above range, the wiring circuit board 1 can improve the transmission efficiency of high-frequency signals and can achieve thinning.

[0057] The covering insulating layer 4 is a porous resin layer 10. The porous resin layer 10 of the covering insulating layer 4 has the same structure (independent bubble structure), physical properties (porosity, average pore size and dielectric constant) and material (resin) (preferably polyimide resin) as the porous resin layer 10 of the base insulating layer 2.

[0058] In cross-section, the shielding layer 5 covers the outer peripheral surface of the base insulating layer 2 and the outer peripheral surface of the cover insulating layer 4. Specifically, the shielding layer 5 is disposed on one side of the base insulating layer 2 in the thickness direction and on both sides in the width direction, and on one side of the cover insulating layer 4 in the thickness direction and on both sides in the width direction. The shielding layer 5 disposed on one side of the base insulating layer 2 in the width direction and the shielding layer 5 disposed on one side of the cover insulating layer 4 in the width direction are continuous in the thickness direction. The shielding layer 5 disposed on the other side of the base insulating layer 2 in the width direction and the shielding layer 5 disposed on the other side of the cover insulating layer 4 in the width direction are continuous in the thickness direction. Therefore, the shielding layer 5 has a frame shape that is approximately rectangular in cross-section.

[0059] In addition, shielding layer 5 is a ground layer (grounding layer), and is grounded at one end in the transmission direction not shown (it is at zero potential).

[0060] The thickness T4 of the shielding layer 5 is, for example, 0.01 μm or more, preferably 0.1 μm or more, and also, for example, 18 μm or less, preferably 12 μm or less. Furthermore, in cross-section, the thickness T4 of the shielding layer 5 is approximately the same throughout the entire circumference of the base insulating layer 2 and the entire circumference of the covering insulating layer 4. The ratio (T4 / T0) of the thickness T4 of the shielding layer 5 to the thickness T0 of the wiring circuit board 1 is, for example, 0.1 or less, preferably 0.01 or less, more preferably 0.001 or less, and also, for example, 0.0001 or more. Additionally, the ratio (T4 / T3) of the thickness T4 of the shielding layer 5 to the thickness T3 of the conductor layer 3 is, for example, 1 or less, preferably 0.1 or less, more preferably 0.01 or less, and also, for example, 0.0001 or more.

[0061] The material of shielding layer 5 is the same as that of conductor layer 3. Shielding layer 5 is a solid, dense layer. Therefore, the porosity of shielding layer 5 is essentially 0%.

[0062] Next, refer to Figure 2 A~ Figure 2 F illustrates an example of the manufacturing method of the wiring circuit board 1. Furthermore, the following steps are performed, for example, according to the contents described in International Publication No. 2018 / 186486.

[0063] like Figure 2 As shown in Figure A, in this method, firstly, a shielding layer 6 on the other side and a base insulating layer 2 disposed on one side of the shielding layer 6 in the thickness direction are prepared. Furthermore, the shielding layer 6 on the other side is a layer included in the shielding layer 5, and is a portion disposed on the other side of the base insulating layer 2 in the thickness direction. It is possible to prepare a laminate formed by pre-laminating the base insulating layer 2 onto the shielding layer 6 on the other side. Alternatively, it is also possible to first prepare the shielding layer 6 on the other side, and then dispose of the base insulating layer 2 on one side of the shielding layer 6 in the thickness direction.

[0064] like Figure 2 As shown in B, in this method, the conductor layer 3 is then disposed on one side of the substrate insulating layer 2 in the thickness direction. For example, the conductor layer 3 having wiring 13 is formed on one side of the substrate insulating layer 2 in the thickness direction by an additive or subtractive method.

[0065] like Figure 2 As shown in C, in this method, the covering insulating layer 4 is disposed on one side of the base insulating layer 2 in the thickness direction in a manner that covers the conductor layer 3.

[0066] like Figure 2 As shown in D, in this method, a side shielding layer 7 is then disposed on one side of the covering insulating layer 4 in the thickness direction. For example, the side shielding layer 7 is formed on the entire surface of one side of the covering insulating layer 4 in the thickness direction by means of plating, sputtering, or the like. Furthermore, the side shielding layer 7 is a layer contained in the shielding layer 5, and is the portion disposed on one side of the covering insulating layer 4 in the thickness direction.

[0067] like Figure 2As shown in E, in this method, an opening 8 is formed in the other side shielding layer 6, the base insulating layer 2, the cover insulating layer 4, and the one side shielding layer 7. Specifically, the opening 8 is formed in the region of the other side shielding layer 6, the base insulating layer 2, the cover insulating layer 4, and the one side shielding layer 7 that does not overlap with the conductor layer 3 when projected along the thickness direction. Two openings 8 are provided such that the conductor layer 3 is sandwiched when projected along the thickness direction. The opening 8 is, for example, a slit that penetrates the other side shielding layer 6, the base insulating layer 2, the cover insulating layer 4, and the one side shielding layer 7 in the thickness direction. In addition, the opening 8 extends along the transmission direction. As a result, a wiring circuit board 1 (a wiring circuit board 1 on which the shielding layer 5 has not yet been formed on the side) is defined inside the opening 8. The wiring circuit board 1 is separated from the outer portion that is outside the opening 8.

[0068] To form the opening 8, for example, a laser, a cutting saw, a drill bit, etc. can be used.

[0069] like Figure 2 As shown in F, next, in this method, side shielding layers 9 are formed on both sides of the base insulating layer 2 in the width direction and on both sides of the covering insulating layer 4 in the width direction. Furthermore, the side shielding layer 9 is a layer included in the shielding layer 5. The method of forming the side shielding layer 9 is the same as the method of forming the one-sided shielding layer 7. The other end of the side shielding layer 9 in the thickness direction is continuous with both ends of the other side shielding layer 6 in the width direction. One end of the side shielding layer 9 in the thickness direction is continuous with both ends of the one-sided shielding layer 7 in the width direction. Thus, a shielding layer 5 composed of the other side shielding layer 6, the one-sided shielding layer 7, and the side shielding layer 9 is formed. Furthermore, in Figure 2 In F, the interface between the shielding layer 6 on the other side and the side shielding layer 9, as well as the interface between the shielding layer 7 on one side and the side shielding layer 9, are clearly shown in shielding layer 5. However, it is also possible that they are not clear and the interfaces cannot be observed.

[0070] Thus, a wiring circuit board 1 having a base insulating layer 2, a conductor layer 3, a cover insulating layer 4, and a shielding layer 5 is obtained.

[0071] like Figure 1 As shown, the thickness T0 of the wiring circuit board 1 is, for example, 600 μm or less, preferably 300 μm or less, more preferably 200 μm or less, and also, for example, 10 μm or more. The width W0 of the wiring circuit board 1 is, for example, 100 μm or more, preferably 600 μm or less. The ratio (T0 / W0) of the thickness T0 of the wiring circuit board 1 to the width W0 of the wiring circuit board 1 is, for example, 6 or less, preferably 3 or less, more preferably 1 or less, and also, for example, 0.1 or more.

[0072] For example, the thickness T1 of the substrate insulating layer 2 is 50 μm, the thickness T2 of the cover insulating layer 4 is 50 μm, and the length L1 of one side portion 11 and the length L2 of the other side portion 12 of the substrate insulating layer 2 in the thickness direction are both 100 μm. Furthermore, the porosity of the porous resin layer 10 of the substrate insulating layer 2 and the cover insulating layer 4 is 80%, and both have an independent bubble structure composed of polyimide resin. When a 10 GHz high-frequency signal flows through the conductor layer 3 with a thickness T3 of 12 μm and a width W3 of 50 μm, the transmission loss of the wiring circuit board 1 with a thickness T0 of 112 μm is, for example, less than 5 dB / 100 mm, preferably less than 4 dB / 100 mm, more preferably less than 3 dB / 100 mm, and even more preferably less than 2.5 dB / 100 mm. Therefore, the high-frequency signal transmission characteristics of this wiring circuit board 1 are excellent.

[0073] <Effects of the First Embodiment>

[0074] In this wiring circuit board 1, since the base insulating layer 2 and the cover insulating layer 4 are porous resin layers 10, the transmission efficiency of high-frequency signals can be improved.

[0075] Furthermore, since the base insulating layer 2 and the cover insulating layer 4 of the wiring circuit board 1 are layered, a thinner profile can be achieved.

[0076] Furthermore, if the ratio of the thickness T2 of the covering insulating layer 4 to the thickness T1 of the base insulating layer 2 is 0.9 or more and 1.1 or less, the distance T1 from the shielding layer 6 (the shielding layer 5 facing the base insulating layer 2) to the conductor layer 3 can be made substantially the same as the distance T2 from the shielding layer 7 (the shielding layer 5 facing the covering insulating layer 4) to the conductor layer 3. Therefore, the influence of the magnetic field from one side in the thickness direction on the conductor layer 3 can be used to counteract the influence of the magnetic field from the other side in the thickness direction on the conductor layer 3. Thus, the influence of external magnetic fields on the conductor layer 3 can be suppressed. As a result, the wiring circuit board 1 can further improve the transmission efficiency of high-frequency signals.

[0077] The wiring circuit board 1 can be better used as a transmission cable to replace coaxial cables.

[0078] <Modifications of the First Embodiment>

[0079] In the following variations, the same reference numerals are used for components and processes identical to those in the first embodiment, and detailed descriptions are omitted. Furthermore, in each variation, unless otherwise specified, the same effects as in the first embodiment can be achieved. Moreover, the first embodiment and its variations can be appropriately combined.

[0080] Alternatively, the base insulating layer 2 may not be a porous resin layer 10, but a dense resin layer (non-porous resin layer). Or, the covering insulating layer 4 may not be a porous resin layer 10, but a dense resin layer (non-porous resin layer). In short, it is acceptable as long as either the base insulating layer 2 or the covering insulating layer 4 is a porous resin layer 10.

[0081] Preferably, as in the first embodiment, both the substrate insulating layer 2 and the cover insulating layer 4 are porous resin layers 10. With the first embodiment, the transmission efficiency of high-frequency signals can be further improved, and further thinning can be achieved.

[0082] like Figure 3 As shown, the conductor layer 3 can include multiple wirings 13. The multiple wirings 13 are arranged at intervals between each other in the width direction. Preferably, the multiple wirings 13 are equally spaced in the width direction. The spacing S between adjacent wirings 13 is, for example, 5 μm or more, preferably 10 μm or more, and also, for example, 100 μm or less, preferably 50 μm or less. Furthermore, the ratio (W3 / S) of the width W3 of the wiring 13 to the spacing S of adjacent wirings 13 is, for example, 0.9 or more, preferably 0.95 or more, and also, for example, 1.1 or less, preferably 1.05 or less.

[0083] <Second Implementation>

[0084] In the second embodiment, the same reference numerals are used for components and processes identical to those in the first embodiment, and detailed descriptions are omitted. Furthermore, the second embodiment, unless otherwise specified, can achieve the same effects as the first embodiment. Moreover, the first embodiment, its variations, and the second embodiment can be appropriately combined.

[0085] Reference Figure 4 The second embodiment of the wiring circuit board of the present invention will be described below.

[0086] like Figure 4 As shown, the covering insulating layer 4 includes an adhesive layer 15 and a porous resin layer 10. The covering insulating layer 4 includes the adhesive layer 15 and the porous resin layer 10 sequentially towards the thickness direction. Preferably, the covering insulating layer 4 only includes the adhesive layer 15 and the porous resin layer 10.

[0087] The adhesive layer 15 is disposed on one side of the substrate insulating layer 2 in the thickness direction, covering the conductor layer 3. The adhesive layer 15 contacts both the thickness-direction side and the width-direction sides of the conductor layer 3, and also contacts the portion of the thickness-direction side of the substrate insulating layer 2 that does not overlap with the conductor layer 3 when projected along the thickness direction (specifically, one side portion 11 and the other side portion 12). The thickness-direction side of the adhesive layer 15 is parallel to the thickness-direction side of the substrate insulating layer 2. The width-direction sides of the adhesive layer 15 are respectively flush with the width-direction sides of the substrate insulating layer 2. In cross-section, the adhesive layer 15 has a roughly U-shaped (Japanese コ) form, open towards the other side in the thickness direction.

[0088] The material of the adhesive layer 15 is not particularly limited; for example, hot-melt adhesives, thermosetting adhesives, and other types of adhesives can be cited. Examples of such adhesives include acrylic adhesives, epoxy adhesives, and silicone adhesives. A material with a low dielectric constant is preferred for the adhesive layer 15. Projected along the thickness direction, the thickness T5 of the portion of the adhesive layer 15 overlapping the conductor layer 3 is, for example, 2 μm or more, preferably 5 μm or more, and also, for example, 100 μm or less, preferably 15 μm or less. The ratio (T5 / T2) of the thickness T5 of the adhesive layer 15 to the thickness T2 of the covering insulating layer 4 is, for example, 10 or less, preferably 1 or less, and also, for example, 0.01 or more, preferably 0.1 or more. If the size of the porous resin layer 10 is within the above range, the wiring circuit board 1 can improve the transmission efficiency of high-frequency signals and achieve a thinner profile.

[0089] The porous resin layer 10 in the covering insulating layer 4 is disposed on one side of the adhesive layer 15 in the thickness direction. Specifically, the porous resin layer 10 is in contact with the entire surface of one side of the adhesive layer 15 in the thickness direction. The porous resin layer 10 in the covering insulating layer 4 has a generally rectangular shape when viewed in cross-section in the width direction. The two sides of the porous resin layer 10 in the width direction are flush with the two sides of the adhesive layer 15 in the width direction. The thickness T6 of the porous resin layer 10 is the distance T6 between one side of the adhesive layer 15 in the thickness direction and one side of the porous resin layer 10 in the thickness direction. The thickness T6 of the porous resin layer 10 in the covering insulating layer 4 is, for example, 10 μm or more, preferably 25 μm or more, and also, for example, 100 μm or less, preferably 75 μm or less. The ratio (T6 / T5) of the thickness T6 of the porous resin layer 10 in the covering insulating layer 4 to the thickness T5 of the adhesive layer 15 is, for example, 0.1 or more, preferably 0.5 or more, and also, for example, 10 or less, preferably 5 or less. The ratio (T6 / T2) of the thickness T6 of the porous resin layer 10 to the thickness T2 of the covering insulating layer 4 is, for example, 1 or less, preferably 0.9 or less, and also, for example, 0.05 or more, preferably 0.5 or more. If the size of the porous resin layer 10 is within the above range, the wiring circuit board 1 can improve the transmission efficiency of high-frequency signals and achieve a thinner profile.

[0090] Next, refer to Figure 2 B and Figure 5 A~ Figure 5 D will be used to illustrate an example of the manufacturing method of the wiring circuit board 1 according to the second embodiment. Furthermore, the following steps can be performed, for example, according to the contents described in International Publication No. 2018 / 186486.

[0091] like Figure 2 As shown in Figure B, firstly, in this method, a shielding layer 6, a substrate insulating layer 2, and a conductor layer 3 are prepared on the other side. Then, as... Figure 5 As shown in Figure A, an adhesive layer 15 is disposed on the substrate insulating layer 2 and the conductor layer 3. For example, a varnish of the adhesive is applied to the substrate insulating layer 2 and the conductor layer 3 and then allowed to dry. Alternatively, the adhesive layer 15 pre-formed on the surface of the release sheet is transferred to the substrate insulating layer 2 and the conductor layer 3.

[0092] like Figure 5 As shown in Figure A, a shielding layer 7 on one side and a porous resin layer 10 disposed on the other side of the shielding layer 7 in the thickness direction are also prepared. It is possible to prepare a laminate formed by pre-laminating the porous resin layer 10 on the other side of the shielding layer 7 in the thickness direction. Alternatively, it is also possible to first prepare a shielding layer 7 on one side, and then dispose of the porous resin layer 10 on the other side of the shielding layer 7 in the thickness direction.

[0093] like Figure 5 A's arrow and Figure 5 As shown in B, in this method, the porous resin layer 10 is then brought into contact with the adhesive layer 15. Specifically, the other side of the porous resin layer 10 in the thickness direction is brought into contact with the other side of the adhesive layer 15 in the thickness direction. Thus, the porous resin layer 10 covering the insulating layer 4 is bonded to the conductor layer 3 and the base insulating layer 2 by means of the adhesive layer 15. Simultaneously, a covering insulating layer 4 comprising the porous resin layer 10 and the adhesive layer 15 is formed.

[0094] like Figure 5 As shown in C, in this method, an opening 8 is formed on the other side shielding layer 6, the base insulating layer 2, the covering insulating layer 4 (adhesive layer 15, porous resin layer 10) and the one side shielding layer 7.

[0095] like Figure 5 As shown in D, next, in this method, a side shielding layer 9 is formed. The side shielding layer 9 is formed on both sides of the base insulating layer 2 in the width direction and on both sides of the covering insulating layer 4 in the width direction. Furthermore, a side shielding layer 9 is also formed on both sides of the adhesive layer 15 of the covering insulating layer 4 in the width direction.

[0096] Thus, a wiring circuit board 1 is obtained, which has a base insulating layer 2, a conductor layer 3, a cover insulating layer 4 and a shielding layer 5. The cover insulating layer 4 has a porous resin layer 10 and an adhesive layer 15.

[0097] <Effects of the Second Embodiment>

[0098] Using this wiring circuit board 1, a porous resin layer 10 can be formed on the covering insulating layer 4, and the porous resin layer 10 can be easily bonded to the base insulating layer 2 and the conductor layer 3 by means of an adhesive layer 15. Therefore, the wiring circuit board 1 can be obtained using a simple method.

[0099] <Modifications of the Second Embodiment>

[0100] In the following variations, the same reference numerals are used for components and processes identical to those in the second embodiment described above, and detailed descriptions are omitted. Furthermore, in each variation, unless otherwise specified, the same effects as those in the second embodiment can be achieved. Moreover, the first embodiment, the second embodiment, and their variations can be appropriately combined.

[0101] like Figure 6 As shown, conductor layer 3 can contain multiple wirings 13.

[0102] Alternatively, firstly, the adhesive layer 15 is disposed on the other side of the porous resin layer 10 covering the insulating layer 4 in the thickness direction, so that the adhesive layer 15 contacts the substrate insulating layer 2 and the conductor layer 3. Figure 5 A is not depicted.

[0103] Furthermore, the above-described invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and not intended to limit the scope of the invention. Modifications of the invention that will be apparent to those skilled in the art are contained in the foregoing claims.

[0104] Industrial availability

[0105] Wiring circuit boards can be used as transmission lines for transmitting signals.

[0106] Explanation of reference numerals in the attached figures

[0107] 1. Wiring circuit board; 2. Substrate insulating layer; 3. Conductor layer; 4. Cover insulating layer; 5. Shielding layer; 10. Porous resin layer; 15. Adhesive layer.

Claims

1. A wiring circuit substrate characterized by comprising: a base insulating layer; a conductor layer disposed on one side of the base insulating layer in a thickness direction; a cover insulating layer disposed on one side of the base insulating layer in the thickness direction so as to cover the conductor layer; and a shielding layer disposed on the other side of the base insulating layer in the thickness direction and on both sides of the base insulating layer in a width direction, and disposed on one side of the cover insulating layer in the thickness direction and on both sides of the cover insulating layer in the width direction, at least one of the base insulating layer and the cover insulating layer has a porous resin layer, a distance Tl between the other side of the conductor layer in the thickness direction and the other side of the base insulating layer in the thickness direction is 10 μm or more and 75 μm or less, a ratio T2 / Tl of a distance T2 between one side of the conductor layer in the thickness direction and one side of the cover insulating layer in the thickness direction to the distance Tl between the other side of the conductor layer in the thickness direction and the other side of the base insulating layer in the thickness direction is 0.9 or more and 1.1 or less, a thickness T4 of the shielding layer with respect to a thickness T3 of the conductor layer, that is, T4 / T3 is 0.1 or less.

2. The wiring circuit substrate according to claim 1, characterized in that the porous resin layer has an independent bubble structure.

3. The wiring circuit substrate according to claim 1, characterized in that a porosity of the porous resin layer is 50% or more.

4. The wiring circuit substrate according to claim 1, characterized in that a material of the porous resin layer is a polyimide resin.

5. The wiring circuit substrate according to claim 1, characterized in that the base insulating layer and the cover insulating layer are composed of the porous resin layer.

6. The wiring circuit substrate according to claim 1, characterized in that the base insulating layer is composed of the porous resin layer, the cover insulating layer has: an adhesive layer which is in contact with one side of the conductor layer in the thickness direction and both sides of the conductor layer in the width direction, and which is in contact with a portion of one side of the base insulating layer in the thickness direction which does not overlap the conductor layer when projected in the thickness direction; and the porous resin layer which is in contact with one side of the adhesive layer in the thickness direction. ​

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